Bacterial wilt is a devastating disease of potato and can cause an 80% production loss. To control wilt using bacteriophage therapy, we isolated and characterized twelve lytic bacteriophages from different water sources in Kenya and China. Based on the lytic curves of the phages with the pathogen Ralstonia solanacearum, one optimal bacteriophage cocktail, P1, containing six phage isolations was formulated and used for studying wilt prevention and treatment efficiency in potato plants growing in pots. The preliminary tests showed that the phage cocktail was very effective in preventing potato bacterial wilt by injection of the phages into the plants or decontamination of sterilized soil spiked with R. solanacearum. Eighty percent of potato plants could be protected from the bacterial wilt (caused by R. solanacearum reference strain GIM1.74 and field isolates), and the P1 cocktail could kill 98% of live bacteria spiked in the sterilized soil at one week after spraying. However, the treatment efficiencies of P1 depended on the timing of application of the phages, the susceptibility of the plants to the bacterial wilt, as well as the virulence of the bacteria infected, suggesting that it is important to apply the phage therapy as soon as possible once there are early signs of the bacterial wilt. These results provide the basis for the development of bacteriophagebased biocontrol of potato bacterial wilt as an alternative to the use of antibiotics.

Aflatoxin contamination in maize by Aspergillus spp. is a major problem causing food, income and health concerns. A study was carried out in Kaiti District in Lower Eastern Kenya to evaluate the effect of three months storage of maize in triple-layer hermetic (PICS™) bags on the population of Aspergillus spp. and levels of aflatoxin. Postharvest practices by maize farmers including time of harvesting, drying and storage methods were obtained with a questionnaire. Aspergillus spp. in soil and maize were isolated by serial dilution-plating and aflatoxin content was measured using Vicam method. Maize was mostly stored in woven polypropylene (PP) and sisal bags within granaries and living houses. Aspergillus flavus L-strain was the most predominant isolate from soil (Mean = 8.4 x10 2 CFU/g), on the harvested grain (4.1 x 10 2 CFU/g) and grain sampled after three months of storage (1.1 x 10 3 CFU/g). The type of storage bag significantly (P ≤ 0.05) influenced the population of members of Aspergillus section Flavi, with A. flavus (S and L strains) and A. parasiticus being 71% higher in PP bags than in PICS bags. Total aflatoxin in maize sampled at harvest and after three months storage ranged from <5 to 42.7 ppb with 55% lower aflatoxin content in PICS bags than in PP bags. After storage, the population of Aspergillus section Flavi was positively correlated with aflatoxin levels. The results of this study demonstrate that PICS bags are an effective management option for reducing population of toxigenic Aspergillus spp. and aflatoxin in stored maize.

Soft rot is an economically significant disease in potato and one of the major threats to sustainable potato production. This study aimed at isolating lytic bacteriophages and evaluating methods for and the efficacy of applying phages to control potato soft rot caused by Pectobacterium carotovorum. Eleven bacteriophages isolated from soil and water samples collected in Wuhan, China, were used to infect P. carotovorum host strains isolated from potato tubers showing soft rot symptoms in Nakuru county, Kenya. The efficacy of the phages in controlling soft rot disease was evaluated by applying individual phage strains or a phage cocktail on potato slices and tubers at different time points before or after inoculation with a P. carotovorum strain. The phages could lyse 20 strains of P. carotovorum, but not Pseudomonas fluorescens control strains. Among the 11 phages, Pectobacterium phage Wc5r, interestingly showed cross-activity against Pectobacterium atrosepticum and two phage-resistant P. carotovorum strains. Potato slice assays showed that the phage concentration and timing of application are crucial factors for effective soft rot control. Phage cocktail applied at a concentration of 1 9 10 9 plaque-forming units per milliliter before or within an hour after bacterial inoculation on potato slices, resulted in C 90% reduction of soft rot symptoms. This study provides a basis for the development and application of phages to reduce the impact of potato soft rot disease.

Limited nitrogen (N) content in the soil is a major challenge to sustainable and high crop production in many developing countries. The nitrogen fixing symbiosis of legumes with rhizobia plays an important role in supplying sufficient N for legumes and subsequent nonleguminous crops. To identify rhizobia strains which are suitable for bioinoculant production, characterization of rhizobia is a prerequisite. The objective of this study was to assess the morphological and genetic diversity of rhizobia that nodulates cowpea in agricultural soils of lower eastern Kenya. Twenty-eight rhizobia isolates were recovered from soil samples collected from farmers' fields in Machakos, Makueni, and Kitui counties in lower eastern Kenya and characterized based on morphological characteristics. Thirteen representative isolates were selected and characterized using BOX repetitive element PCR fingerprinting. Based on the dendrogram generated from morphological characteristics, the test isolates were distributed into two major clusters at a similarity of 75%. Phylogenetic tree, based on BOX repetitive element PCR, grouped the isolates into two clusters at 90% similarity level. The clustering of the isolates did not show a relationship to the origin of soil samples, although the isolates were genetically diverse. This study is a prerequisite to the selection of suitable cowpea rhizobia to develop bioinoculants for sustainable crop production in Kenya.

PurposeThe paper is an excerpt from a bigger study with an overall aim of examining the extent to which climate change adaptation has been integrated in the EIA studies undertaken in Kenya since the process inception in 2000. The purpose was to establish whether adequate attention is given to the issue of climate change mitigation as major challenge in the world during the 21st century.Design/methodology/approachThe research design is based on qualitative research involving a review of EIA reports approved by the national environmental authority and also based on key informant consultations with licensed EIA experts in the country. Thereafter, the findings were analyzed through standard statistical procedures.FindingsThe findings showed that climate change integration in all the reviewed EIA reports was mainly restricted to mere consideration of historical climate change information in the project areas and totally weak in terms of climate change prediction scenarios and their likely impacts on the proposed development projects. However, consultations with most EIA practitioners indicated that integration of climate change adaptive capabilities into the EIA process was a relevant issue but admitted that the implementation modalities were unclear.Originality/valueThe study is the first in evaluating the level of integration for climate change in EIA studies in Kenya and the findings will inform EIA implementation in the country. It also forms a good basis for comparative studies with EIA studies in other countries of the world.

The biodiversity characteristics in eight small (0.065-0.249 km 2 ) public man-made reservoirs in the central part of the Eastern Rift Valley, Kenya, were studied between 1995 and 1998. A total of 71 phytoplankton species belonging to approximately 50 taxa were identified. Chlorophytes and cyanobacteria dominated the crop. The dominant taxa included Botryococcus, Syunura, Microsystis, Anabaena, and Cosmarium. A total of over 40 zooplankton species were identified. The community was composed mainly of crustacea, rotifers and protozoa. The most dominant group was Keratella but Brachionus and Nauplius were equally abundant. The diversity and abundance of benthic invertebrates was not high, and only 18 species were identified throughout the study period with the range of species number being 1-7 per reservoir. The benthic fauna was mainly composed of Lumbriculidae and Chironomid worms. A total of six monthly bird counts found an average of 60 birds per reservoir, and a total of 49 species was identified. Ducks, geese and coots dominated the waterfowl, especially during the dry season. Largescale breeding by Black-headed Heron (Ardea melanocephala) and Little Egret (Egretta garzetta) was observed in one of the sites, and other species were also breeding in the reservoirs. The population of waterbirds in reservoirs was closely related to the biomass of benthic invertebrates, and the findings of the study indicate that the structure and dynamics of life forms within small man-made reservoirs can serve as excellent sensors and indicators of the state of watershed health.

<p class="1Body">Water is an important good provided by watersheds and is critical in sustaining life and socio-economic development. This study evaluated water provision in the Chyulu Hills watershed which is one of the important dry land water catchments in Kenya. Surface water discharge was mainly through rivers and springs with the latter being more prevalent than the former while ground water provision was primarily through boreholes and shallow wells. Springs discharged the highest water volume annually estimated at 128.14million m³ or 85.14% of all the water discharged in the watershed, with shallow wells and boreholes discharging the least water. For all the springs found in the watershed, Mzima springs discharged the highest water volume estimated at nearly 113.15 million m³ annually or 88.30% of the water produced by all the springs; and about 75.19% of the water in the entire watershed. Rivers which were active had a total water discharge of about 20.66million m³ per year, with Kibwezi River discharging 17.59 million m³ annually or 85.14% of all the water from rivers. Shallow wells were mainly prevalent at Nthongoni and the Makindu, and their annual water discharge was about 16.96million m³ per year with boreholes contributing 98.87% (approximately 16.76 million m³/yr.) of the ground water, and the rest (19,169.92m³/yr.) being contributed by shallow wells. The total amount of water discharged in the watershed by the combined water source types was about 150.49 million m3/yr.</p>

Nitrogenase activity (acetylene reduction activity) was found to occur universally in the Cyperus papyrus swamp in Lake Naivasha. Low rates of acetylene reduction activity (0 .9-104 .9 nmol C 2H 4 g d.wt . roots -' h -1 ) were associated with excised roots of C . papyrus but higher rates of activity (89 .0-280 .4 nmol C 2H4 g d .wt . roots -1 h -') were associated with intact root systems of the plant . It was estimated that nitrogen fixation associated with young roots alone could supply about 26% of the nitrogen requirements of growing papyrus plants . Acetylene reduction activity in the lake bottom sediments was generally low and associated with adjacent papyrus stands . Plate counts of putative aerobic and facultatively anaerobic N 2-fixing bacteria associated with papyrus roots showed the presence of high numbers of diazotrophs (5 .4 x 106 CFU g d .wt . roots -') . Fewer numbers of N 2-fixing bacteria were detected in the sediments (1 .9 x 103-3.2 x 10 4 CFU g d .wt . sediment -1 ).